CFD Analysis of Particulate Flow for Enhanced Air Quality using OpenFOAM and PALM model system

Abstract

Particulate matter (PM) degrades air quality in both outdoor and indoor environments and poses health risks because its small size enables deposition in the respiratory tract. This issue is especially important for indoor air quality (IAQ) since people may spend more than 20 hours per day indoors. Outdoor PM exposure is also critical; residing within 300-500 m of main roads is linked to reduced lung capacity and increased cardiovascular mortality. Motivated by these concerns, this study combines three investigations of particle behavior and control: particle deposition in a rib-roughened channel with a deflector: an inclined plate to redirect the flow and particles toward the rough elements, the effect of a single noise barrier on near-road aerosol dispersion under varying wind conditions, and the influence of dual noise barriers on nearby and on-road air quality. The first study uses a Eulerian-Lagrangian framework with the Launder, Reece and Rodi (LRR) turbulence model and Lagrangian particle tracking to simulate particulate flow in a rib-roughened channel. Results show a deflector increases deposition by enhancing particle interaction with the lower wall, but this deposition-enhancing effect comes with an increased pressure drop from flow blockage. The second and third studies, using continuous spatial fields of total particle number concentration and wind velocity at an urban highway site, find that barriers reduce downwind concentrations under low winds but can worsen local air quality under strong crosswinds: deceleration forms a high-concentration windward plume that is lofted upward and dispersed downstream. The third study identifies two mechanisms: flow-barrier interaction and a highway recirculation zone that transports particles to higher altitudes and reduce air quality in downwind areas. Together the studies quantify how engineered structures, from small deflectors to large noise barriers, modify particle transport and deposition.